The present invention relates to a nozzle which can be attached to a steam outlet of a coffee machine. Especially for coffee machines adapted to produce a cappuccino-style coffee it is known to provide a water steam outlet which is cooperating with a supply of milk such that hot frothed milk can be produced.
In order to generate frothed milk, a defined amount of air is usually sucked into the stream of milk and steam.
When carrying out this frothing repeatedly, the nozzle will eventually be contaminated with the residues of heated milk which are prone to bacterial contamination. Correspondingly it is well known that ideally after each use such a frothing nozzle should be rinsed and cleaned.
From U.S. Pat. No. 6,499,389 B1 a device for producing milk froth for cappuccino is known, having a nozzle arrangement that is disposed downstream of a steam pipe and has a vacuum chamber, into which a milk supply line terminates. An air conduit connects to the milk supply lines upstream of the vacuum chamber. An emulsifying chamber is disposed downstream of the vacuum chamber, with the emulsifying chamber having a chamber wall, a floor with a central, flow-diverting protrusion and an outlet. The central, flow diverting protrusion is embodied as a flow trap surrounding the outlet in the flow such that the protrusion diverts a mixture essentially to a direction of flowing in the primary flow direction essentially countered to the primary flow direction. U.S. Pat. No. 6,499,389 furthermore teaches (see column 3, lines 50 to 55) that the elements of the emulsifying chamber can be made of a half-hard synthetic material, notably chloroprene caoutchouc (“neoprene”). This synthetic material has sufficient dimensional stability when exposed to hot steam. On the other hand due to the complex design and the costs of the materials used for this known device it cannot be produced with reasonable costs in order to serve as a disposable nozzle which is replaced after a limited number of uses.
WO 2004/054413 A1 proposes a nozzle adaptable to a steam outlet of a coffee machine and designed to froth a liquid. The nozzle thereby is made of one single piece and comprises an opening for a steam supply, a restriction in the extension of said opening, and an enlarged zone in the axis of said restriction. Said opening provides an outlet for the liquid, having a cross-section substantially equal to the cross-section of the opening. Perpendicular to the opening a conduit for supply of the liquid and an air inlet is provided.
According to this known prior art the nozzle can be made for example from a polypropylene (PP) plastics material or from a metal, such as for example Inox. It is said that this known nozzle can be used throughout the typical use cycles of an entire day.
One problem that is experienced in practice with the devices of the prior art is that the device tends to cause the product or steam to splash, in particular, in conditions where there is a shortage of milk. For instance, when the milk supply becomes depleted, the ratio of steam to milk increases (for more steam) which so induces a too energetic flow of steam or mixture that comes out of the device. This is a critical issue, as the flow of steam tends to dirty the place, either directly by simply splashing in an uncontrolled manner or indirectly by blowing out the milk froth already made in the cup.
U.S. Pat. No. 5,295,431 relates to an accessory for the preparation of a creamy air-milk-steam emulsion with anti-splashing means being positioned at one side outlet of a first flow means. Such a device has several disadvantages. The open configuration on a side of the accessory is not suitable because in order, to be effective, the anti-plashing chamber must be large enough to allow the frothed liquid to swirl in the chamber before exiting the chamber. Therefore, this configuration is bulky and not economically and environmentally adapted for a disposable application after a limited number of uses.